Furnace for burning wet fuels



July 8, 1952 E. l.. DENNIS 2,602,409

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July 8, 1952 E. 1 DENNIS FURNACE FOR BURNING WET FUELS Original Filed Sept. 26, 1947 5 Sheets-Sheet 2 July 8, 1952 E. l.. DENNIS FURNACE FOR BURNING WET FUELS Original Fled Sept. 26, 1947 3 Sheets-Sheet 3 glu/umm 0 w/A/ L. DENN/.5

Patented July 8, 1952 2,602,409 FURNACE FOR. BURNING WETFUELS Edwin L. Dennis, Baton Rouge, La., assignor to Riley Stoker Corporation,

Worcester, Mass., a

corporation of Massachusetts Original application September Divided and 2.6, 1947, Serial this application March 1s, 1949, serial No. 81,699 s claims.l (c1. 11oi) AThis, invention relates to furnaces, and more particularly to the construction and arrangement of furnaces for burning waste materials such as ,bagasse wood refuse, and the like, which are relatively high in moisture content. This application is a division of my prior application Serial No. 776,381, filed September 26, 1947,-which application has become abandoned.

Heretofore it has been a common practice to burn such fuels in a so-called horse shoe furnace from which the -hot gases travel over the top of -a bridge Wall and thus into a. main combustion chamber formed b y the setting of a steam boiler. The fuel-burning capacity of suc a ,construction is decidedly limited. Furthermore, large quantities of fly ash are carried over the bridge wall and accumulate on the floor of the main combustion chamber, where they fuse into ahard glassy mass. A great amount of labor is required for the removal of this mass, and it is `-necessary to shut down the boiler and allow the setting to cool before such work can be started. Accordingly the boiler may be out of service for long periods at rather frequent intervals.

These diiiiculties have been recognized, and an attempt has been made to overcome them by burning the fuel within the boiler setting and directly beneath the boiler tubes. However, such arrangements as heretofore employed have proven to be incapable of burning sufficient fuel to operate 'the boiler at more than a relatively small fraction of its full capacity. Thus it has been necessary to install more boilers than would be required if each boiler could be depended upon to vgenerate its full quota of steam. Furthermore, it is important to provide for firing the boiler with an auxiliary fuel, such as oil, in order to maintain a supply of steam during a temporary shortage of the waste fuel. Oil and similar fuels, however, are burned in suspension and rev quire considerable furnace volume and provision for ample flame travel. With the prior constructions it has not been found possible to comply with these requirements, and the oil burning capacity *has been extremely limited.

Itis accordingly one object of the invention to provide a furnace capable of burning combustible waste materials such as bagasse, wood refuse, and the like in `an eiiicient manner and at relatively 'high rates.

Itis a. Vfurther object of the invention to provide a vfurnace .construction and ,arrangement adapted for use with asteam boiler and capable of burning high moisture-solid fuels at rates sufficiently high to operate the boiler at its maximum steam generating capacity.

It is a further object of the invention to provide a furnace construction and arrangement adapted to burn high moisture solid fuels at rates required for the operation of an associated steam boiler at its maximum steam generating capacity, the furnace also being capable of burning o il inramounts required for the generation of large quantities ofsteam when the principal fuel is in short supply.

With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification' and covered by the claims appended hereto.

Referring to the drawings illustrating one embodiment of the invention, and in which like reference numerals indicate like parts,

Fig. 1 isa longitudinal section through a steam generating furnace, vtaken on the line I-I of Fig. 3;

Fig. 2 is a section taken on the line 2--2 of Fig. 1;

Fig. 3 is a section taken on the line 3--3 of Fig. 1;

Fig. 4 is a section taken on the line 4-4 of Fig. 3;

Fig. 5 is a perspective view of an air nozzle;

Fig. 6 is a fragmentary plan view through an air nozzle and the adjacent refractory material;

Fig. 7 is an enlargement of a portion of Fig. V2;

Fig. 8 is a section taken substantially on the line 8-8 of Fig. 7; and

Fig. 9 is a view similar to Fig. 3 showing a slightly modiiied construction.

The embodiment illustrated comprises a steam generator having an upper transverse steamand-water drum I0 and a lower transverse water drum II therebeneath, the drum II being located a substantial distance above a floor I2. The drums I0 and Il are connected by a rear bank rof upright water tubes Ill and by a front bank -of upright water tubes I5. A transverse header or small drum I6 is mounted at a substantial distance in front of the upper drum I0. The :lower drum II is connected to the front drum IB vby a bank of generally L-shaped tubes vIii arranged in three transverse rows. These tubes I8 have upright lower portionsl I9 located closely in front of the tubes I5, and substantially horizontal upper portions 20 which preferably slope slightly upwardly toward the front drum I6. Two rows of tubes Z2 connect the front drum I6 to the steamand-water drum I0.

The steam generating parts as so far described are mounted within a setting constructed largely of refractory material. This setting includes a front wall 24 adjacent to the front drum I5, a rear wall 25 behind the tubes I4, two side walls 26, and a roof 28. This roof is supported by the upper row of tubes 22.

The space 30 beneath the upper portions 20 of the tubes I8 forms a combustion chamber of considerable height and volume from which hot gases may now upwardly. To direct these gases in a desired path a baille 3| extends upwardly from the lower drum II between the tube banks I5 and I8 to the bends in the tubes I8 and thence forwardly part way along the uppermost of the tube portions 20. Another baiile 33 extends downwardly from the upper drum I adjacent to the front portion of the tube bank I4, and terminates somewhat above the lower drum II. With this construction the gases ow upwardly fromV the combustion chamber 30 past the front edge of the baiile 3|, thence rearwardly and downwardly between the bales 3l and 33, thence rearwardly and upwardly between the baille 33 and the rear wall 25 to an outlet duct 34 behind the steam-and-water drum I0. A fly ash hopper 35 is provided between the lower drum Il andthe rear wall 25. Y

Provision is made for burning waste solid fuel directly beneath the combustion chamber 353.

For this purpose there are provided a plurality of fuel burning cells arranged in two transverse rows in the lower portion of the boiler setting. As shown, there are two front cells 38 and two rear cells 39, each cell having a restricted gas outlet opening or throat 4I! at its upper end communicating directly with the combustion chamber 30 thereabove. The front walls of the front cells 38 are formed by the lower portion of the front wall 24, and the outer side walls of all four cells are formed by the lower portions of the side walls 25. The rear walls of the rear cells 39 are formed by a wall 42 located adjacent to the lower drum I I and slightly in front thereof. The front cells 38 are separated from the rear cells 3S by a transverse Wall 43, and the right hand cells 38-39 are separated from the left hand cells 38-39 by a longitudinal wall 44. Fuel is supplied to the cells 38 and 39 through chutes 45 (Fig. 4) which lead to openings 4l in the side walls 26. Ashes are removed from the cells through openings 48 in the front wall 24 and the rear wall 42, these openings being provided with suitable doors 49.

The piles of fuel in the cells 3B and 39 are burned by means of air which is directed against each pile through openings in the cell walls. For this purpose the walls of each cell are made hollow to provide a primary air chamber I which extends around the cell and for a substantial distance upwardly above the level of the cell floor. The several air chambers 5I are separated from one another by upright metal plates 52 with their edges embedded in the adjacent brickwork. A multiplicity of air nozzles 54 are built into the refractory walls of each cell to conduct air from the corresponding chamber 5I into the cell interior. These nozzles may be metal castings, and as shown in Figs. 5 and 6 they are of squarecross section externally, each nozzle having a tapered longitudinal passage 55 therethrough.

The hotV gases from the burning fuel travel upwardly through the restricted throats 40. In order to ensure complete combustion of these gases, jets of secondary air are discharged in tangential directions into each throat, these air Vwall 42 between the two rear cells 39.

jets tending to whirl the gases and create considerable turbulence therein. As shown, the wall around each throat 4l! is made hollow to provide an annular air chamber 5l which is connected to the throat by tangentially arranged nozzles 58. These may be of similar construction to the nozzles 54. The secondary air chambers 57 are separated from one another, and upright metal plates 59 may be used for this purpose Wherever there is insufficient space available for a brickwork partition.

Air under pressure is supplied to each of the air chambers 5I and 5l, with independent manual control of the air supply to each chamber. In the embodiment illustrated a turbo-blower EI of well known construction is mounted on the front wall 24 between the two front cells 33, and a similar turbo-blower 6I is mounted on the rear Each blower discharges air directly into a metal casing 63 (Figsv'l and 8) built into the brickwork. This casing has two openings 64 leading upwardly into the adjacent upper air chambers 5l, and two Vopenings E leading downwardly into the adjacent lower air chambers 5I. Each upper opening 54 is controlled by a damper 5l having an operating rod 58, and each lower opening 65 is controlled by a damper i9 having an operating rod ll.

The large combustion chamber 39 may be used to burn an auxiliary fuel in suspension. For this purpose the front wall 24 is provided with an opening I3 for a suitable oil burner 'I4 above each of the front cells'38. There is ample space available for the flames from these burners to travel rearwardly and complete the combustion lof the oil before reaching the first row of L-shaped tubes I8. Y

The operation of the invention will now be apparent from the above disclosure. Each of the cells 38 and 39 will be supplied with fuel such as bagasse, Wood refuse, or the like through the chutes 45 and the openings '4l by gravity. Each cell will contain a fuel pile generally conical in shape, with jets of primary air from the nozzles- 54 directed against the sides of the pile to maintain combustion. The vhot gases from each burning pile will travel upwardly through the restricted throat 45 thereabove, where secondary air jets from the nozzles 58 will enter the gases from tangential directions. This will whirl the gases, creating extreme turbulence, and promoting a rapid and thorough mixture which v/ill ensure substantially complete combustion before 'f the gases reach the horizontally inclined portions D 2U of the Water tubes.

The gases will thereupon travel upwardly across the tube portions 29, downwardly in contact with the tubes I5 behind the baille 3l, and upwardly in contact with the tubes 2 I4 behind the baille 33, finally escaping through the outlet 34. Fly ash which escapes from the combustion chamber 30 with the gases will for the most part be deposited in the hopper 36, from which it will be removed as required. Steam will be generated in a well-known manner in the water tubes I8, 22 and I5, the steam being discharged into the drum III and withdrawn therefrom for use. The turbo-blowers El supply air under pressure to the air chambers 5l and 51 under the control of the dampers 79 and 81 respectively. Thus the operator can control vthe air to each fuel-burning cell independently of the others, and he can also vary the ratio of the primary air to the secondary air. After a considerable quantity of fuel has been burned in any particular cell, the fuel supply thereto will be stopped and the pile allowed to burn down, whereupon the incombustible residue will be raked out through the door opening 48, and the cell can again be placed in service. The boiler can be red with oil by means of the burners 'I4 whenever there is an insufficient supply of bagasse or other solid fuel to meet the demand for steam.

In Fig. 9 there is shown a sectional plan view, similar to Fig. 3 but on asmaller scale, of a modified construction suitable for use with a wider boiler. This embodiment comprises a front wall 24', two side walls 2'6, and a rear wall 42. Three front cells 38 are provided, and two rear cells 39', each cell having a cleanout door 49. Each cell is surrounded by a primary air chamber 5| from which nozzles 54 direct air jets into the cells. The air chambers are separated by upright plates 52. It will be clear that fuel may readily be chuted to the middle front cell 38 through the front wall 24', but since the boiler would interfere with any chute through the rear wall 42'. it is not considered feasible to provide more than two rear cells 39'. 'Io compensate for their lack of numbers, the rear cells are shown wider than the front cells.

It will now be apparent that the invention provides a furnace in which the fuel burning capacity is in much better proportion to the capacity of the associated steam boiler than has been the case with any construction heretofore available for use with wet fuels such as bagasse, wood refuse, and the like. The four or more vertical cells will burn sufficient fuel to operate the associated steam boiler at substantially its full capacity, and the cells can easily be cleaned one at a time, whenever required, without any necessity for shutting down the boiler or for allowing the setting to cool off. These results are facilitated by the novel construction of the individual fuel burning cells and their arrangement in two transverse rows beneath the associated L-shaped tubes I8. By this means I provide the large furnace volume which is essential to complete the combustion of the gases and solid combustible particles carried upwardly with them through the throats 40. This combustion space is also available for the burningv of oil in adequate amounts to produce large quantities of steam whenever the principal fuel is for any reason in short supply. Furthermore the shape of the tubes I8 is such as to reduce the absorption of heat radiating from the cells, and this aids combustion by increasing the temperature within the cells. The restricted throats 40 further contribute to this result by appreciably shielding the cell interiors from the water tubes. The tangentially positioned air nozzles 58 cause the gases owing upwardly from the cells to enter the combustion chamber 30 with very pronounced whirling movements, so that the gases within the said chamber are in a very turbulent condition 6 which is conducive to rap-id and efficient combustion.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A furnace comprising upright walls forming a combustion chamber of considerable height having a gas outlet adjacent its upper end, walls forming two transverse rows of fuel burning cells directly beneath the combustion chamber and opening upwardly Vinto the combustion chamber, means to supply fuel to each cell and form a pile of fuel therein, the walls of each cell having openings therein for the discharge of air into the cell to burn the fuel, each cell being provided with an outlet throat at its upper end which throat 1s smaller in cross-section in all lateral dimensions than the corresponding dimensions of the cell, and tangentially directed openings provided in the walls of the throat for the discharge of air jets into the gases flowing upwardly through the throat to whirl the gases. l

2. A furnace comprising upright walls forming a combustion chamber of considerable height having a gas outlet adjacent its upper end, walls forming a fuel burning cell directly beneath the combustion chamber and having an outlet throat which is smaller in cross-section in all lateral dimensions than the corresponding dimensions of the cell at its upper end for the vupward. discharge of hot gases, and means to supply fuel to the cell and form a pile of fuel therein, the walls of the cell having openings adjacent the lower portion of the cell for the-discharge of air against the said pile and other openings adjacentr the throat for discharge of air tangentially into lthe hot gases flowing upwardly throughV the REFERENCES CITED vThe following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 17,842 Longacre July 21, 1857 211,082 Bennett Jan. 7, 1879 268,682 Jackson Dec. 5, 1882 407,703 Sutcliffe July 23, 1889 455,173 Cook June 30, 1891 1,657,698 Schutz Jan. 31, 1928 1,952,010 Gregory Mar. 20, 1934 2,114,619 Ward Apr. 19, 1938 

